Under certain operating conditions aircraft are vulnerable to the accumulation of ice on component surfaces. It is well known that such accumulation of ice can lead to disastrous results. A wide variety of systems have been developed for removing ice from aircraft during flight and can be placed into three general categories: thermal, chemical and mechanical.
The mechanical category of deicing systems operate by distorting the airfoil surface of the aircraft to be deiced. Distortion of the airfoil surface causes cracking in the ice accumulated thereon and subsequent dispersal of that ice into the air stream passing over the aircraft component.
U.S. Pat. No. 4,690,353 to Haslim et al. and commonly owned U.S. Pat. No. 4,875,644 to Adams et al. describe a subcategory of mechanical deicing systems wherein one or more overlapped flexible ribbon conductors are embedded in an elastomeric material affixed to the outer surface of an airfoil structure. The conductors are fed large current pulses from a power storage unit. The conductors are configured such that overlapping conductors carry opposing currents. The resulting interacting magnetic fields of these overlapping conductors produces an electro-expulsive force which distends the elastomeric member and separates the elastomeric member from a solid body, such as ice accumulated thereon. The preferred method in Haslim et al. to provide overlapping conductors having opposing currents traveling therethrough is to form the conductor in a serpentine like configuration. Adams et al. discloses an improvement upon the disclosure of Haslim et al., wherein rather than having a serpentine type configuration, Adams et al. contemplates having electrically conductive members interconnected such that any electrical current flowing in the conductive members flows in the same direction in adjacent electrically conductive members in a first sheet-like array and also flows in adjacent electrically conductive members of a second sheet-like array in a direction opposite to the current flowing in the first sheet-like array. The first and second sheet like arrays are therefore coextensive and superposed proximate to each other such that the electrically conductive members of the first and second sheet like arrays are substantially parallel. It was found in Adams et al. that the configuration of the conductive members into sheet like arrays provided a much greater expulsive force than that provided by the serpentine type conductive configuration of the Haslim et al. disclosure.
It has been discovered however, that it is both difficult and expensive to manufacture conductors in the arrangements disclosed in Haslim et al. and Adams et al. The continuous conductive members in both of these patents must be formed or machined from a solid piece of conductor, or ribbon cable into a twisting, turning, folding shape. Forming these types of conductive members is labor intensive and therefore quite expensive to manufacture. Another disadvantage to the conductive members disclosed in Haslim et al. and Adams et al. is the weak point created when the conductive members are folded. Extensive use of the conductive members described therein causes fatigue and eventual breaking of the conductive member at the fold.
Another disadvantage of the conductor arrangements disclosed in Haslim et al. and Adams et al. is the absence of a fail safe mechanism in the event of a failure of the conductor (i.e. an open). A failure of the conductor at any point in the configuration therefore results in a failure of the total system, which can be disastrous under certain conditions. Also, it is advantageous in electro-expulsive deicing systems to maintain the resistance of the conductive elements as low as possible.
A low resistance electro-expulsive separation deicing system which overcomes the above identified disadvantages is, therefore, highly desirable.